In such fields as underground mining, need arises for on-site splicing of sections of cables which have become separated by reason of mishandling or other abuse common to that environment. In these fields, several approaches have found acceptance, providing for a seamless electrical insulator to extend over the crimped connection of the cables and onto the surfaces of the cable insulation. In one of these approaches, use is made of heat-shrinkable insulator having a diameter exceeding that of the cable insulation and, accordingly, readily applied to the body of one of the cables to be joined and, likewise, easily movable into position over the crimped connection and onto the surfaces of the cables. When so positioned, heat is applied to the insulator, causing same to tightly grip all underlying surfaces and to provide a watertight covering for the splice. Additionally, this type of covering exhibits sufficient strength for cable reeling purposes and otherwise resembles quite closely the original cable insulation in shape and mechanical and electrical properties. The disadvantages attending use of the foregoing heat-shrinking insulators include the time-consuming need for application of heat on-site and deterioration of insulating material by overheating. Additionally, the available materials for heat-shrink application are of limited flexibility.
Another approach in present use involves a prestretched tubing type of insulator, inclusive of an additional element, arranged interiorly to the stretched tubing and sufficiently self-sustaining to retain the tubing in stretched condition. Typically, the interior member is in the form of a continuous strip arranged in hollow circular configuration. Once the assembly is placed over a splice to be insulated, the strip member is withdrawn, whereupon the tubing collapses to its original condition, snugly engaging the splice and associated cables. The disadvantages attending this second approach are several. Since the tubing is typically an elastomer, and since the interior member remains in continuous pressure relationship with the elastomer until the point of use, the elastomer frequently takes a set and fails to fully recover its original diameter after long stretching periods. In addition, pre-stretching of the tubing is required to be in excess of the range intended by reason of the presence of the interior member. The removal of the interior member on site gives rise to several difficulties, predominant among which is the consumption of substantial time in the course of removal of the interior member. The uncoiling of the interior member further generally limits application to circular cross-section. Frequently, the uncoiled interior member engages a protrusion, for example, a corner of the ferrule of the splice, which prevents the interior member from further uncoiling and results in an incomplete operation.
A third approach involves the use of an outer member of self-sustaining hollow configuration for retaining insulative tubing in stretched condition. The tubing is stretched within the outer member and an adhesive is employed to bond the stretched tubing to the inner wall of the outer member. The outer member is frangible and is shattered when the expanded tubing is in position over a cable splice. Thereupon, a solvent is introduced through the shattered outer member to release the bond thereof with the tubing. While this approach has advantage in not requiring excess pre-stretching of the tubing to accommodate an inner self-sustaining member and in not involving removal of such inner member, disadvantage remains in that the tubing is in pre-stretched state from the point of product manufacture to point of use. Also, use of the adhesive limits shelf life. Further, toxic solvents are needed for release, presenting difficulty in confined environments. There is also the matter of time consumption in directing solvent into the bonded areas of shattered outer member and relaxed tubing.